An IPA vowel diagram approach to analysing L1 effects on vowel production and perception

This paper examines the influence of the first language on the accuracy with which trained phoneticians judge isolated monophthongs taken from the phoneme systems of two different languages. The main finding of this study was that the speaker’s as well as listener’s L1 background have a significant influence on judgements which were made by means of the IPA vowel diagram. This paper consists of 6 sections. In section (1) we will recall the basic principles of the IPA vowel diagram focusing on its layout, proportions, and primary cardinal vowels. In section (2) we will refer to the tradition of using the cardinal vowel system in phonetic studies, particularly in order to plot a vowel sound at a certain point within the space of the IPA vowel diagram. In section (3) we will suggest how the influence of the L1 on articulation and perception of vowels of an unknown language can be investigated with the help of the IPA vowel diagram. The methods which we used during the preparation of recordings and perception experiment, as well as subjects who took part in them, will be described in section (4) and a presentation of the main results will follow in section (5). Finally, we will discuss the results with respect to the three basic dimensions of the vowel sounds: height, backness and rounding. 1. IPA VOWEL DIAGRAM AND CARDINAL VOWELS The IPA vowel diagram represents an abstract vowel space, which in its layout and proportions is derived from the one which had been used in the cardinal vowel system of Daniel Jones (e.g. Jones 1962 [1]). It has parallel top and bottom (hence a trapezium), right angles at top and bottom back and ratio 2:3:4 (base:back:top). This is the most simplified version of the figure developed by Jones through a number of stages, in which articulatory accuracy was progressively sacrificed for practical convenience in drawing the diagram (Ashby 1989 [2]). Layout and proportions of the vowel diagram are set in the IPA Handbook in accordance with the Kiel convention of 1989 [3]. The vowels are plotted on the diagram with reference to certain fixed points. Daniel Jones proposed a series of 8 (primary) cardinal vowels, spaced around the outside of the possible vowel area and designed to act as fixed reference points for phoneticians (Ladefoged 1993 [4], p. 219). The space within the diagram represents a continuum of possible vowel qualities which have to be identified by their relationships to the cardinal vowels. According to Daniel Jones a scale of these 8 cardinal vowels forms a convenient basis for describing the vowels of any language (Jones & Ward 1969 [5]). Therefore any vowel pair of different qualities can be described as occupying different positions within the space of the diagram and can be identified by their relationships to the cardinal vowels (Lisker 1989 [6], p. 24). 2. USE OF THE IPA VOWEL DIAGRAM IN PHONETIC STUDIES The cardinal vowel system has been extensively used by phoneticians in the description of a wide variety of languages (Ladefoged 1993 [4], p. 220). The description of vowel qualities with the help of the vowel diagram requires a phonetician to be able to position them as certain points on the diagram. The three basic dimensions, height, backness and rounding, together with the values of cardinal vowels are involved in making a decision on the position of the vowel quality within the space of the diagram. Obviously, the values of the cardinal vowels must be known to both the phoneticians originally plotting the vowels and to the phoneticians who are going to interpret the descriptions. Daniel Jones’s idea was that the values of cardinal vowels cannot be learnt by written descriptions; they should be learnt by oral instruction from a teacher who knows them (Jones 1962 [1], p. 34). Consequently, a phonetician has to be capable of distinguishing many more vowel qualities than there are in his own language and of judging the degree of their similarity. His doing so indicates that his L1 vowels are like known places on a map, and that he is making a phonetic judgement in stating the distance between one of his own vowels and a vowel pronounced by another speaker (Ladefoged 1967 [7], p. 55). In this way the question as to what phoneticians should be aware of when they describe a vowel sound by plotting it at a certain point on the vowel diagram seems to be answered as follows: one could discriminate and plot a vowel sound correctly, if (i) the three basic dimensions of the vowel sounds, (ii) the values of cardinal vowels, and (iii) the layout and proportions of the IPA vowel diagram are well known and taken into consideration in making a final decision on the position of the vowel in the diagram. 3. ARTICULATION AND PERCEPTION OF VOWEL SOUNDS ON THE IPA VOWEL DIAGRAM If we agree upon an assumption that phonetically trained subjects have knowledge of and experience with the three basic dimensions of vowel sounds and are aware of the values of the cardinal vowels on the IPA vowel diagram, then we should expect them to be able to produce almost any vowel sound plotted as a certain point within the space of the diagram. At least this can be assumed to be the case for the L1 vowels of the subject, as he is naturally well-trained in them. In order to evaluate this hypothesis we could record a sequence of prototypical vowels taken from the phoneme systems of two different languages which have been elicited through specification of a number of anonymous points on the IPA vowel diagram. We would then present them for auditory judgement to a panel of equally qualified subjects. The recorded vowels would be judged according to their phonetic qualities and plotted back on the vowel diagram, which shows only the cardinal vowel symbols for orientation. Consequently, it can be expected that the points obtained in such a way should almost exactly match the initial points of the vowel sounds on the diagram. If one of the subjects produced the above mentioned sequence of vowels and after that judged them, then we could investigate whether his own judgements show significantly smaller deviations from the intended vowel qualities than the judgements of other subjects. Let us refer here to the fact that the proportions and layout of the IPA vowel diagram are a result of Daniel Jones’s intention to achieve a practical convenience in drawing the diagram despite the articulatory inaccuracy of the devised figure. Therefore the IPA vowel diagram is an ’impressionistic’ tool which does not have a well defined relationship to any one physical domain (Nolan 1988 [8]). Furthermore, the problem of how and where to position a particular vowel sound on the IPA diagram was a matter of discussion during the meeting in Kiel in 1989. A necessity to explicitly determine the process underlying the decision of phoneticians to plot this or that point representing a particular vowel sound was expressed (Nolan 1988 [8]). Thirteen years have past since the Kiel Convention of 1989 [3]; a new generation of phoneticians has been giving oral instructions to students on how to pronounce and perceive vowel sounds analytically, i.e. independently from their L1, and how to use the IPA vowel diagram in phonetic studies. By means of a perception experiment whose methods and subjects will be described in the next section we have tried to gain a clear understanding of the difficulties which could result from using the IPA vowel diagram in phonetic studies as well as from oral instructions by a teacher who is a speaker of a particular language. 4. EXPERIMENTAL PROCEDURE 4.1. Subjects A total of four female subjects took part in both recordings and perception experiment. Two of them were native speakers of German and two were native speakers of Russian. At the time of the recordings all subjects were on the scientific staff of departments of phonetics in Germany and Russia. All subjects had graduated from the departments they were working at. They were phonetically trained and had already gained some experience in teaching phonetics. All subjects were aged 25 to 35. 4.2. Stimuli Fourteen of the 20 initial points were taken from the “Handbook of the IPA” [9]. They represented the prototypical positions of 14 vowel phonemes of German on the diagram (see the filled dots in fig. 1). The other six points represented the prototypical positions of the vowel phonemes of Russian (see the open dots in fig. 1). They were taken from the “Phonetics of modern Russian” used recently in phonetic classes in Russia (Bondarko 1988 [10]) since the phoneme system of Russian is not included in the “Handbook of the IPA”. The subjects were unaware of the fact that the presented points corresponded to the positions of the vowel sounds of their own language as well as of a second language which they did not speak. The sequence of points was randomized in a way that would prevent tuning of the subjects to the three basic dimensions of vowel sounds (height, backness, rounding). 4.3. Recordings The recordings were carried out in sound treated rooms at the departments of phonetics in Germany and Russia. Each of the four subjects produced 20 vowel sounds corresponding to the initial prototypical positions on the IPA vowel diagram. J J J J J J J J J J J J J J J J J B B B B B B B B B B B B B B B B B i